A census is conducted to systematically gather information about the members of a population. The composition of a population refers to its structure in terms of factors like sex, age, occupation, literacy levels, income, and health. It provides information on the number of males and females in different age groups, their education levels, employment, income, and health status. The population pyramid illustrates the age and sex structure, while the sex ratio measures the number of females per 1000 males. India's 2011 census showed a sex ratio of 940 females per 1000 males.